1. Field of the Invention
The present invention relates to a CPP (current perpendicular to the plane) type magnetic detecting element. Particularly, the present invention relates to a magnetic detecting element permitting a decrease in the effective element size while maintaining a large optical element size, and an effective and easy improvement in reproduction output, and a method of manufacturing the magnetic detecting element.
2. Description of the Related Art
FIG. 28 is a sectional view of the structure of a conventional magnetic detecting element, as viewed from a surface facing a recording medium.
The spin valve magnetic detecting element shown in FIG. 28 comprises a multilayer film 9 comprising an antiferromagnetic layer 2, a pinned magnetic layer 3, a nonmagnetic material layer 4, a free magnetic layer 5, a nonmagnetic material layer 6, a pinned magnetic layer 7, and an antiferromagnetic layer 8, which are laminated in that order from the bottom, electrode layers 1 and 10 formed above and below the multilayer film 9, hard bias layers 11 formed on both sides of the free magnetic layer 5, insulating layers 12 formed below the hard bias layers 11, and insulating layers 13 formed above the hard bias layers 11.
The antiferromagnetic layers 2 and 8 are made of PtMn, the pinned magnetic layers 3 and 7 and the free magnetic layer 5 are made of a ferromagnetic material such as NiFe or the like, the nonmagnetic material layers 4 and 6 are made of Cu, the hard bias layers 11 are made of a hard magnetic material such as CoPt or the like, the insulating layers 12 and 13 are made of alumina, and the electrode layers 1 and 10 are made of a conductive material such as Cr.
The magnetic detecting element shown in FIG. 28 is referred to as a “dual spin-valve magnetic detecting element” in which the nonmagnetic material layer 4 and the pinned magnetic layer 3 are formed below the free magnetic layer 5, and the nonmagnetic material layer 6 and the pinned magnetic layer 7 are formed above the free magnetic layer 5, for detecting a recording magnetic field from the recording medium such as a hard disk or the like.
The magnetic detecting element shown in FIG. 28 is a CPP (current perpendicular to the plane) type magnetic detecting element in which an electric current flows in a direction perpendicular to the film plane of each of the layers of the multilayer film 9.
The magnetization direction of each of the pinned magnetic layers 3 and 7 is pinned in the Y direction shown in the drawing, and the magnetization direction of the free magnetic layer 5 with no external magnetic field applied thereto is oriented in the track width direction (the X direction shown in the drawing) in a single magnetic domain state by longitudinal bias magnetic fields from the hard bias layers 11. When the external magnetic field is applied, the magnetization direction of the free magnetic layer 5 changes to change the electric resistance of the multilayer film 9. The change in the electric resistance is converted to a voltage change or current change to detect the external magnetic field.
It is generally known that the CPP type magnetic detecting element cannot effectively produce high reproduction output unless the track width Tw and the length MRh in the height direction are 0.1 μm or less (i.e., the element area is 0.01 μm2 or less), as compared with a CIP (current in the plane) type in which a sensing current flows in parallel to the film plane of each layer of the multilayer film).
Therefore, a construction is conceivable, in which as shown in FIG. 28, a current limiting layer 14 comprising a mixture of an insulating portion and a conductive portion is overlapped with the multilayer film 9, for flowing the sensing current only through the conductive portion to narrow the current.
The sensing current flowing from an electrode layer into the free magnetic layer 5 of the multilayer film 9 through the current limiting layer 14 locally flows through a portion of the free magnetic layer 5 corresponding to the conductive portion to locally increase the current density in this portion.
It is thus expected that the element area (referred to as an “effective element area”) where the sensing current actually flows through the free magnetic layer 5 to contribute to a magnetoresistive effect can be made smaller than the element area of the free magnetic layer 5 (referred to as an “optical element area”) in parallel to the film plane.
In the conventional magnetic detecting element shown in FIG. 28, the current limiting layer 14 is laminated above or below the antiferromagnetic layer 8 or 2.
The antiferromagnetic material such as PtMn used for forming the antiferromagnetic layers 2 and 8 has high resistance. Therefore, the mean free path of conduction electrons flowing through each of the antiferromagnetic layers 2 and 8 is short, and thus the conduction electrons in the narrow path diffuse due to inelastic scattering, thereby decreasing the effect of locally concentrating the current density by the current limiting layer 14. As a result, the problem of a difficulty in increasing ΔR of the magnetic detecting element occurs.